Natural materials are anticipated as renewable materials. However, differentiation must be conducted to ensure quality, and this requires many years of mastery. So, the author have investigated a differentiation method which analyzes the results of infrared spectroscopic analysis utilizing exploratory data analysis of chemometrics and which does not require mastery. Exploratory data analysis refers to principal component analysis and hierarchical cluster analysis. With linen and ramie as materials, the author investigated the measurement method, principle component analysis conditions, validity of the population data, etc. As a result, the author measured with KBr tablet method, performed first derivation on the permeability, and it was possible to differentiate linen fibers from ramie fibers by analyzing up to analytical wavenumber ranging 850～1050cm^-1 and third principle component.

Mechanical properties of polyurethane foam are very important for designing comfortable cushioning material for home furnishings use. In this study, compression-recovery property, compression stress relaxation property and compression creep property of eight kinds of polyurethane foam are investigated experimentally. Shape of sample used is a continuous mat of 5cm thickness for compression-recovery test, and an assembly of 1cm cubic for compression viscoelastic test. Results are obtained as follows:

(1) Compression-recovery properties of polyurethane foam are divided into three types; i.e. high elastic polyurethane foam, low elastic polyurethane foam, and intermediate elastic polyurethane foam.

(2)Stress-strain curve of low elastic polyurethane foam has a flection point at around 1.500-1.700 Pa. At the flection point, large tangential elasticity turns to low.

(3) Compression relaxation behavior of low elastic polyurethane foam has two stages.

(4) Expression of compression stress relaxation for polyurethane foam is obtained as follows: σ = βt^-α, where, σ (Pa): stress at time t (s); α and β are constants.

(5) Compression creep behavior of low elastic polyurethane foam has two stages. Expression of compression creep displacement for intermediate polyurethane foam is obtained as follows: ε_t = Y₀ ln(vt+1), where, Y₀ (mm) and v (s^-1) are constants.